How to reinstall UEFI grub in a disk, where I only can legacy-boot using another disk?

I went over many posts, books, blogs on Grub, UEFI,... and I can't figure out how to fix my grub. Situation: My main disk (SSD 500GB, now in /dev/sda) run debian using Grub2 in UEFI. All good. After messing, now I have two disks running debian: 1- previous one (SSD running debian), not booting anymore in UEFI or Legacy 2- an WD disk (1TB in /dev/sdc) running Debian 11 contains legacy MBR and grub From grub in legacy I can run WD-Debian 11 or SSD-Debian Computer does not boot in UEFI I want to switch my system back to UEFI. However I can't boot as UEFI, no grub starts in UEFI. lsblk: NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT. sda 8:0 0 447.1G 0 disk ├─sda1 8:1 0 512M 0 part ├─sda2 8:2 0 414.7G 0 part └─sda3 8:3 0 31.9G 0 part sdb 8:16 0 7.3T 0 disk sdc 8:32 0 931.5G 0 disk ├─sdc1 8:33 0 930.6G 0 part / ├─sdc2 8:34 0 1K 0 part └─sdc5 8:37 0 976M 0 part [SWAP] I tried to install grub in sda, (sudo grub-install /dev/sda): But got error: > Installing for i386-pc platform. grub-install: warning: this GPT partition label contains no BIOS Boot Partition; embedding won't be possible. grub-install: error: embedding is not possible, but this is required for cross-disk install. I tried to use debian live, gparted live, etc but I could not find grub-install in these live iso. How could I rescue the grub in UEFI mode in my SSD disk? Thanks